As pressure mounts for the intelligence community to curb its surveillance activities or at least make them more transparent, a key National Security Agency official will testify before the Senate Appropriations Committee on Wednesday.

Army Gen. Keith Alexander, National Security Agency director and head of U.S. Cyber Command, will testify before the full committee in a previously-scheduled session, marking the first time an NSA official will answer to Congress in public since news broke that the agency is collecting all of Verizon's U.S. phone records, as well as internet content from non-U.S. internet users abroad.